The invention relates to a method for encoding objects in a traffic route network, to which information from one transmitter at a time to a receiver is transmitted, and for the encoding and decoding of which different databases, in particular digital maps of the traffic route network, can be used in the transmitter and the receiver.
For transmitting location-specific information, such as traffic reports, various methods have become known. In the TMC (Traffic Message Channel), for instance, a location is transmitted on the basis of a location code. Its geographic location and thus also the local association of the report are made possible only by a so-called location database in the receiver. For navigation purposes, digital road maps are used, in which the individual locations and other objects are identified by their geographic location and by their road connections. For transmitting arbitrary location-specific information to receivers which include a suitable database, encodingxe2x80x94also known as referencingxe2x80x94with the aid of a geographic context is therefore increasingly being done. This referencing goes beyond the indication of geographic data, because these data cannot preclude ambiguities (for instance a road under or over a bridge). There can also be differences among databases, for instance from different publishers.
From German Patent Disclosure DE 198 35 051.1, a device for encoding and decoding locations has been disclosed, in which the code includes a declaration and one encoded location each from all the coordinate parts, which location includes a plurality of pairs of coordinates; one pair of coordinates represents the coordinates, stored in memory at the transmitter, of the encoded location, and at least one further pair of coordinates represents at least one auxiliary point, while the declaration part includes at least the number of these pairs of coordinates contained in the coordinate part. With this device, however, it is not readily possible to encode and decode objects that are absent from the receiver database or are not present in it in identical form, especially deviating coordinates.
The object of the present invention is to encode and decode objects that are not present in a receiver database and/or if differences exist between the geographic indications in the databases.
In the encoding method according to the invention, this object is attained in that the objects are each provided with at least one coordinate chain, which is located at least in part on traffic routes that are also included in the database of the receiver and which includes characteristic properties of parts of the traffic route network. The characteristic properties can be prominent courses of the routes, in particular curves, and prominent sequences of intersections, forks and/or curves, or objects which are stored in memory, referenced identically, in each of the databases used.
The method of the invention can for instance be used to transmit information about objects which are not expected to be present in databases of the receivers. Such an object can for instance be a newly erected parking garagexe2x80x94that is, a point-like objectxe2x80x94or together with an access road it can form a coordinate chain. A newly opened bypass road can for instance also be transmitted by the method of the invention and inserted into the database of a receiver. The information about the object can be a location indication per se, such as absolute or relative coordinates and names, other information such as texts, pictures, audio files, video files and internet addresses, or navigation attributes, such as travel directions (one-way streets), primary and secondary roads, and traffic limitations.
Transmitting information by the method of the invention can be done via arbitrary media, such as radio or an air interface (GSM, Bluetooth, WAP), or optical media. The information can also be exchanged via data carriers. Transmissions over various networks (ISDN, Internet) are also possible.
Examples of formats for transmitting the objects can be: the name of the object, coordinates of the first point, coordinates of the second point and so forth, or the name of the object, coordinates of the first point, coordinate differences from the second point, coordinate differences from the third point, and so forth. In the context of such formats, predefined curvy stretches can also be transmitted.
In performing the method of the invention, the coordinates located on flat ground (geographic coordinates, X/Y) are as a rule sufficient as coordinates. However, within the scope of the invention, it is also possible to include the altitude (Z) in the transmission and further processing.
In addition to the aforementioned use for transmitting objects that are not present, or not present in the same form, in the databases of the receivers, further possible uses also exist. For instance, information about locations to avoid, especially because of traffic jams, can be transmitted, or the fact that attributes of locations have changed, for instance so that the travel speeds in congested stretches can be adjusted before a route is calculated. Additional stretches, so-called emergency detours, can also be entered in the digital maps in the databases of the receivers. Attributes can also be added to the digital maps or changed in them, such as street names, service station hours of operation, and objects of interest to tourists or in other ways (POIs=Points of Interest).
The method of the invention can also be used to link two different digital maps to one another, if they have common objects suitable for comparison. In that case the transmitter and receiver need not be separate from one another. In the sense of the method of the invention, a navigation device can for instance serve as a transmitter; such a device has a relatively low-resolution digital map on a replaceable data carrier, while the receiver is the same navigation device, for instance with a more-detailed digital map.
A user of the navigation device is for instance driving toward a large city and is using a CD-ROM with a digital map, which contains only the most-important through roads through the large city. For navigating to a secondary road, the user can replace the CD-ROM with another that has a more-detailed map. If at the time of this manipulation the user""s current location is not listed on this map, then a coordinate chain that contains the current location can be formed with parts of the through roads, and thus the current location and the route to the region shown on the more-detailed map can additionally be entered on that map.
Depending on the embodiment of the applicable part of the traffic route network, the coordinate chain required to achieve nonambiguity in the receiver can be embodied in various ways. To achieve the most optimal possible definition, particularly of as few pairs of coordinates as possible, in a refinement of the method of the invention it is proposed that an ascertained coordinate chain is compared with traffic routes of the database of the transmitter, and if ambiguities result the coordinate chain is varied and/or expanded by additional pairs of coordinates.
To avoid an unnecessary search for parts of the coordinate chain that are not present in the receiver database anyway, in another refinement it is provided that those parts of the at least one coordinate chain for which a match with the database of the receiver is to be expected are especially identified.
An advantageous method for decoding objects that are encoded by the method of the invention is that the coordinate chain that was received with the object is compared with the database of the receiver; that if there are similarities, the at least one coordinate chain is associated with the similar part of the traffic route network; and that in accordance with the geometric location of the associated part, the non-associated parts of the at least one coordinate chain are connected to the traffic routes of the receiver database.
Thus the receiver is also capable of decoding information about locations that are not present in its database and of outputting this information in a suitable form, for instance on a screen or by speech output.
Another use of the decoded information can be that the transmitted object and the parts, adjacent to the object, of the at least one coordinate chain that are not located in the traffic route network stored in memory in the database of the receiver, are entered into the database of the receiver, or entered in a further database.
To accomplish the comparison of the coordinate chain with the traffic routes stored in memory in the receiver database, it is preferably provided that for comparison, methods of pattern recognition (map matching) are employed.